On Wed, Nov 2, 2011 at 6:08 PM, Barry Shein <bzs@world.std.com> wrote:
Another practical problem with this approach is that .IN is India but hey, at least it blocks something :-)
There are also some services out there that block connections entirely, if the user doesn't have a PTR record. I'm thinking IRC servers, MUDs, and some other services with strange security policies that check for a port 113 IDENT response and RDNS to make a dark magic security decision to block a user who has no PTR. But in the modern world... more commonly, MTAs such as sendmail are often configured to require a valid PTR record. So as an ISP, you may be breaking your user's local MTA if you don't have the correct PTR for their IP addresses. So I would say following the RFCs and implementing the proper PTRs will help with that performance issue as a side-effect of having a valid zone, and head off other issues with possibly less popular services that are still blocking connections based on lack of proper PTR. :)
-- -Barry Shein, that'd be .ID for Indonesia
-- -JH